Comtrade tries to estimate quantity or netweight only if country does not report them. That is the reason why unit value varies between reporting countries (or even within the same reporting country; depends on trade flow, partner country, etc).  At part of estimation procedure, Comtrade may use Standard Unit Value (SUV; generated from ...

UN Comtrade reported trade value as is, however trade quantity may be estimated. For this specific case, quantity was estimated using unit value 0.271